^^ on that note...
Definitely don't complain to her in the aspect of it's "her" wanting to eat out all the time that's throwing you off course. All that does is place blame on her.
It's not so much a matter of how 'vain' you are in comparison to her. But in the same regard, a majority of women don't want to feel as though a man pays more attention to himself than he does to her. Vainness is a part of it (women generally DO like to be the ones to take more time getting ready and all that). Women DO like men to take care of themselves. They like that a man WANTS to look good. But there needs to be some give to it also.
When you guys go out to eat, don't make a big deal about "oh man I'm screwing up my body with this!!" Make allowances in your weekly plan so that you CAN have some goodies when you're out with her (like others have advised already). BUT if you order something 'lighter' for the sake of your body instead of getting the deep fried cheese balls or something like that, DON'T make a big production of it to her. If she doesn't work out, she'll only see comments about the quality of food as a criticism of HER wanting to go out to eat.
Yes, chicks are weird like that
So in a nutshell, for the love of GOD, don't complain to her about the food you two eat when you go out (and ESPECIALLY about what SHE eats). And don't blame her for being the reason that you eat 'off plan' here and there.
(disclaimer: not to say that you ARE making it out as though it's HER fault for this. Just make sure you don't make it sound like you are. Especially TO her if she doesn't fully understand the lifting lifestyle.)